A micro-aerobic hydrolysis process for sludge in situ reduction: performance and microbial community structure

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Activated sludge processes generate significant amounts of waste sludge, posing disposal challenges.
• Existing methods for sludge reduction are often inefficient or costly.
• Optimizing microbial communities is key to improving wastewater treatment efficiency and sustainability.

Purpose of the Study:

• To evaluate the effectiveness of a novel Sludge Process Reduction Activated Sludge (SPRAS) system for in-situ sludge reduction.
• To compare the performance of SPRAS with the traditional Anoxic/Aerobic (AO) process.
• To investigate the microbial community structure and its role in sludge reduction within the SPRAS system.

Main Methods:

• Implementation of a Sludge Process Reduction (SPR) module (micro-aerobic tank and settler) before the activated sludge process.
• Operation of SPRAS and AO systems and monitoring of Chemical Oxygen Demand (COD) and ammonium nitrogen removal efficiencies.
• Quantification of sludge production and sludge yield.
• Pyrosequencing analysis to characterize microbial communities in both systems.

Main Results:

• SPRAS system achieved average removal efficiencies of 86.6% for COD and 87.9% for ammonium nitrogen.
• SPRAS process reduced sludge production by 57.9% compared to the AO process, with a sludge yield of 0.076 gVSS/gCOD.
• Pyrosequencing revealed higher relative abundance and stability of microbial communities in SPRAS.
• Enrichment of fermentative acidogenic bacteria (e.g., Anaerolineae, Actinobacteria) in the SPR module and specific genera (e.g., Sulfuritalea, Propionivibrio, Myxobacteria) in the SPRAS system.
• Increased abundance of nitrifying bacteria in the SPRAS system.

Conclusions:

• The SPRAS system is highly effective for in-situ sludge reduction and wastewater treatment.
• The enhanced sludge reduction is attributed to the enrichment of specific fermentative and oxyanion-reducing bacteria within the SPR module.
• SPRAS promotes a more stable and abundant microbial community, including nitrifiers, leading to improved overall system performance.